<!DOCTYPE html>
<html lang="en-US">
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width,initial-scale=1">
    <title>08_变量的基本使用 | 知识库演示</title>
    <meta name="generator" content="VuePress 1.9.9">
    <link rel="icon" href="/vdoing-demo-repository/img/favicon.ico">
    <meta name="description" content="web前端技术博客,简洁至上,专注web前端学习与总结。JavaScript,js,ES6,TypeScript,vue,python,css3,html5,Node,git,github等技术文章。">
    <meta name="keywords" content="前端博客,个人技术博客,前端,前端开发,前端框架,web前端,前端面试题,技术文档,学习,面试,JavaScript,js,ES6,TypeScript,vue,python,css3,html5,Node,git,github,markdown">
    <meta name="theme-color" content="#11a8cd">
    
    <link rel="preload" href="/vdoing-demo-repository/assets/css/0.styles.bb913129.css" as="style"><link rel="preload" href="/vdoing-demo-repository/assets/js/app.52e6b5d0.js" as="script"><link rel="preload" href="/vdoing-demo-repository/assets/js/2.f10ddeba.js" as="script"><link rel="preload" href="/vdoing-demo-repository/assets/js/14.52e25550.js" as="script"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/10.82e086d6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/100.2570dab9.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/101.b429c13f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/102.0e9afba4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/103.42e8d9d6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/104.6ca089b8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/105.f02335fc.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/106.2fe52c32.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/107.7650f18b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/108.7d825011.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/109.42092f8e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/11.49ec595f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/110.8e6f8d5b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/111.84bc1774.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/112.5da6cb16.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/113.2eb6714d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/114.dbdf6a79.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/115.96dc61ac.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/116.2774e841.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/117.5a0ea935.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/118.72005b7a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/119.77fd4a33.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/12.66e2368f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/120.994b6190.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/121.794bec47.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/122.239044f6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/123.d6247b89.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/124.357cddf4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/125.b27c8c6b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/126.2f09d5b4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/127.5b5e7dcc.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/128.ca8342ed.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/129.62196c04.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/13.01d28bf6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/130.ae36e0a1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/131.63408c4f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/132.7a1bc472.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/133.6f365b21.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/134.7dfd70a1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/135.c110453c.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/136.dea9b77b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/137.212998a2.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/138.cf96d5b3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/139.34437df0.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/140.b28a1de4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/141.d117632d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/142.743bfbfc.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/143.d6c926e2.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/144.86916e4e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/145.a4658544.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/146.9f190393.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/147.b53beefe.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/148.d49c882d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/149.b5c8b142.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/15.ff9c9117.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/150.ab4902b7.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/151.aa13cf1a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/152.ca32ca39.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/153.f3dc7a9e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/154.2198d119.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/155.6cf21591.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/156.929b9e50.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/157.6d227e19.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/158.ad6e937f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/159.d74c55e1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/16.a59e9d0e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/160.1e9abdb1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/161.5343ce3e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/162.214b3f61.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/163.918d2361.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/164.204cab40.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/165.884ba632.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/166.e3bc3126.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/167.b8103188.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/168.176b21b8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/169.56e67ae6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/17.73f27920.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/170.05fe9454.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/171.ac72af48.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/172.134bd8be.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/173.f7b83d9b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/174.bc7aa46f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/175.c654668c.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/176.33b09327.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/177.97d7e55f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/178.ab02c611.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/179.0d88c6f5.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/18.39e882fe.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/180.1a2df1f3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/181.533495f7.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/182.a4fc6807.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/183.e3a44f30.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/184.b731d331.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/185.e6eb67ad.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/186.c2493cb4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/187.279befae.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/188.1de7c987.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/189.e748958a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/19.ef7490a3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/190.ad045bc8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/191.c3131762.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/192.29ea4e7e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/193.1e75aa14.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/194.f1150906.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/195.2a593c50.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/196.5aa5efe2.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/197.a328dc59.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/198.9db60424.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/199.d3b39a54.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/20.b5301937.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/200.a9dae555.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/21.2e9bd506.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/22.02e5e5a0.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/23.a00bf08d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/24.dae9e7bf.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/25.3120ccd4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/26.628f5a86.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/27.d4e86439.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/28.642a9f76.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/29.6c013ead.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/3.c3e96c9f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/30.4e45e23b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/31.9b0c4fcb.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/32.347f1a82.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/33.a17e9f72.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/34.ae475141.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/35.70d7eb87.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/36.0166a619.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/37.8d63783a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/38.91c94a9e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/39.edf5fef6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/4.f05e47c1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/40.f2dfda35.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/41.488faa5e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/42.258fde58.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/43.c46a30da.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/44.cfac4a51.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/45.58439e5f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/46.91d42cf4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/47.39ec1b7a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/48.900b1d2a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/49.4db4a295.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/5.85821e9b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/50.4a48e245.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/51.32253e74.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/52.f9692c89.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/53.f93fad53.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/54.cccf7ffb.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/55.7e4f324a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/56.5d04b9d7.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/57.ed34f737.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/58.9e762eed.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/59.81cfbcc1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/6.5f8d8bd6.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/60.76f14de8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/61.a4d207e0.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/62.fce4471e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/63.58fd2153.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/64.b3f081c8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/65.dbde37b1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/66.49bc7970.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/67.48b689d5.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/68.a3660c81.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/69.b4057547.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/7.4acc3e20.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/70.5f3717cf.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/71.d47ff342.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/72.eca3c6ef.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/73.71bbaeec.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/74.6fe6e554.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/75.4dbad835.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/76.6ec52a3f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/77.9041350a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/78.e0b3aa97.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/79.1dbdb52c.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/8.503d9748.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/80.568b41f1.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/81.9394cc64.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/82.e36a0a2e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/83.fba15f4a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/84.1a6a64b4.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/85.af0f0d14.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/86.aed3f80d.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/87.08c34bee.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/88.52b2750e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/89.6d27f363.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/9.9691b37e.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/90.cccb0e61.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/91.6fb1e7f3.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/92.9e3d1d8a.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/93.25bb0c7b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/94.0a896da5.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/95.41991c9b.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/96.1f4103d8.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/97.97ec058f.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/98.f40afd31.js"><link rel="prefetch" href="/vdoing-demo-repository/assets/js/99.ac67e72d.js">
    <link rel="stylesheet" href="/vdoing-demo-repository/assets/css/0.styles.bb913129.css">
  </head>
  <body class="theme-mode-light">
    <div id="app" data-server-rendered="true"><div class="theme-container sidebar-open have-rightmenu"><header class="navbar blur"><div title="目录" class="sidebar-button"><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" role="img" viewBox="0 0 448 512" class="icon"><path fill="currentColor" d="M436 124H12c-6.627 0-12-5.373-12-12V80c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12zm0 160H12c-6.627 0-12-5.373-12-12v-32c0-6.627 5.373-12 12-12h424c6.627 0 12 5.373 12 12v32c0 6.627-5.373 12-12 12z"></path></svg></div> <a href="/vdoing-demo-repository/" class="home-link router-link-active"><img src="/vdoing-demo-repository/img/EB-logo.png" alt="知识库演示" class="logo"> <span class="site-name can-hide">知识库演示</span></a> <div class="links"><div class="search-box"><input aria-label="Search" autocomplete="off" spellcheck="false" value=""> <!----></div> <nav class="nav-links can-hide"><div class="nav-item"><a href="/vdoing-demo-repository/" class="nav-link">首页</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="Python" class="dropdown-title"><a href="/vdoing-demo-repository/python/" class="link-title">Python</a> <span class="title" style="display:none;">Python</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>Python</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/c438df/" class="nav-link">Python基础</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/vdoing-demo-repository/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/802a1ca6f7b71c59/" class="nav-link">Vue</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/javascript/" class="nav-link">《JavaScript教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/es6/" class="nav-link">《ES6 教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/vue/" class="nav-link">《Vue》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/wx-miniprogram/" class="nav-link">小程序笔记</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/vdoing-demo-repository/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/vdoing-demo-repository/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><a href="/vdoing-demo-repository/archives/" class="nav-link">归档</a></div> <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" rel="noopener noreferrer" class="repo-link">
    GitHub
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav></div></header> <div class="sidebar-mask"></div> <div class="sidebar-hover-trigger"></div> <aside class="sidebar" style="display:none;"><!----> <nav class="nav-links"><div class="nav-item"><a href="/vdoing-demo-repository/" class="nav-link">首页</a></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="Python" class="dropdown-title"><a href="/vdoing-demo-repository/python/" class="link-title">Python</a> <span class="title" style="display:none;">Python</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>Python</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/c438df/" class="nav-link">Python基础</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="前端" class="dropdown-title"><a href="/vdoing-demo-repository/web/" class="link-title">前端</a> <span class="title" style="display:none;">前端</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><h4>前端文章</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/8143cc480faf9a11/" class="nav-link">JavaScript</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/pages/802a1ca6f7b71c59/" class="nav-link">Vue</a></li></ul></li><li class="dropdown-item"><h4>学习笔记</h4> <ul class="dropdown-subitem-wrapper"><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/javascript/" class="nav-link">《JavaScript教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/es6/" class="nav-link">《ES6 教程》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/vue/" class="nav-link">《Vue》笔记</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/typescript-axios/" class="nav-link">《TypeScript 从零实现 axios》</a></li><li class="dropdown-subitem"><a href="/vdoing-demo-repository/note/wx-miniprogram/" class="nav-link">小程序笔记</a></li></ul></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="页面" class="dropdown-title"><a href="/vdoing-demo-repository/ui/" class="link-title">页面</a> <span class="title" style="display:none;">页面</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/8309a5b876fc95e3/" class="nav-link">HTML</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/0a83b083bdf257cb/" class="nav-link">CSS</a></li></ul></div></div><div class="nav-item"><div class="dropdown-wrapper"><button type="button" aria-label="技术" class="dropdown-title"><a href="/vdoing-demo-repository/technology/" class="link-title">技术</a> <span class="title" style="display:none;">技术</span> <span class="arrow right"></span></button> <ul class="nav-dropdown" style="display:none;"><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/9a7ee40fc232253e/" class="nav-link">技术文档</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/4c778760be26d8b3/" class="nav-link">GitHub技巧</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/117708e0af7f0bd9/" class="nav-link">Nodejs</a></li><li class="dropdown-item"><!----> <a href="/vdoing-demo-repository/pages/41f87d890d0a02af/" class="nav-link">博客搭建</a></li></ul></div></div><div class="nav-item"><a href="/vdoing-demo-repository/archives/" class="nav-link">归档</a></div> <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" rel="noopener noreferrer" class="repo-link">
    GitHub
    <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></a></nav>  <ul class="sidebar-links"><li><a href="/vdoing-demo-repository/pages/c438df/" class="sidebar-link">01_认识 Python</a></li><li><a href="/vdoing-demo-repository/pages/54ff73/" class="sidebar-link">02_第一个 Python 程序</a></li><li><a href="/vdoing-demo-repository/pages/d84b0c/" class="sidebar-link">03_PyCharm 的初始设置(知道)</a></li><li><a href="/vdoing-demo-repository/pages/d99c19/" class="sidebar-link">04_多文件项目的演练</a></li><li><a href="/vdoing-demo-repository/pages/6bdfff/" class="sidebar-link">05_注释</a></li><li><a href="/vdoing-demo-repository/pages/20b1cf/" class="sidebar-link">06_算数运算符</a></li><li><a href="/vdoing-demo-repository/pages/82298a/" class="sidebar-link">07_程序执行原理(科普)</a></li><li><a href="/vdoing-demo-repository/pages/9b2741/" aria-current="page" class="active sidebar-link">08_变量的基本使用</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/9b2741/#目标" class="sidebar-link">目标</a></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/9b2741/#_01-变量定义" class="sidebar-link">01. 变量定义</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_1-变量演练1-ipython" class="sidebar-link">1) 变量演练1 —— iPython</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_2-变量演练-2-pycharm" class="sidebar-link">2) 变量演练 2 —— PyCharm</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_3-变量演练-3-超市买苹果" class="sidebar-link">3) 变量演练 3 —— 超市买苹果</a></li></ul></li><li class="sidebar-sub-header level2"><a href="/vdoing-demo-repository/pages/9b2741/#_02-变量的类型" class="sidebar-link">02. 变量的类型</a><ul class="sidebar-sub-headers"><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_2-1-变量类型的演练-个人信息" class="sidebar-link">2.1 变量类型的演练 —— 个人信息</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_2-2-变量的类型" class="sidebar-link">2.2 变量的类型</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_2-3-不同类型变量之间的计算" class="sidebar-link">2.3 不同类型变量之间的计算</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_2-4-变量的输入" class="sidebar-link">2.4 变量的输入</a></li><li class="sidebar-sub-header level3"><a href="/vdoing-demo-repository/pages/9b2741/#_2-5-变量的格式化输出" class="sidebar-link">2.5 变量的格式化输出</a></li></ul></li></ul></li><li><a href="/vdoing-demo-repository/pages/3e8319/" class="sidebar-link">09_变量的命名</a></li><li><a href="/vdoing-demo-repository/pages/a02b0a/" class="sidebar-link">10_判断语句</a></li><li><a href="/vdoing-demo-repository/pages/79d78c/" class="sidebar-link">11_运算符</a></li><li><a href="/vdoing-demo-repository/pages/3ce888/" class="sidebar-link">12_循环</a></li><li><a href="/vdoing-demo-repository/pages/ceea69/" class="sidebar-link">13_函数基础</a></li><li><a href="/vdoing-demo-repository/pages/e158a8/" class="sidebar-link">14_高级变量类型</a></li><li><a href="/vdoing-demo-repository/pages/ed6fdd/" class="sidebar-link">15_名片管理系统(综合应用)</a></li><li><a href="/vdoing-demo-repository/pages/e98ba6/" class="sidebar-link">16_变量进阶(理解)</a></li><li><a href="/vdoing-demo-repository/pages/f99095/" class="sidebar-link">17_函数进阶</a></li></ul> </aside> <div><main class="page"><div class="theme-vdoing-wrapper "><div class="articleInfo-wrap" data-v-06225672><div class="articleInfo" data-v-06225672><ul class="breadcrumbs" data-v-06225672><li data-v-06225672><a href="/vdoing-demo-repository/" title="首页" class="iconfont icon-home router-link-active" data-v-06225672></a></li> <li data-v-06225672><a href="/vdoing-demo-repository/python/#Python" data-v-06225672>Python</a></li></ul> <div class="info" data-v-06225672><!----> <div title="创建时间" class="date iconfont icon-riqi" data-v-06225672><a href="javascript:;" data-v-06225672>2023-04-02</a></div> <!----></div></div></div> <!----> <div class="content-wrapper"><div class="right-menu-wrapper"><div class="right-menu-margin"><div class="right-menu-title">目录</div> <div class="right-menu-content"></div></div></div> <h1><img src="">08_变量的基本使用<!----></h1> <!----> <div class="theme-vdoing-content content__default"><h1 id="变量的基本使用"><a href="#变量的基本使用" class="header-anchor">#</a> 变量的基本使用</h1> <blockquote><p><strong>程序就是用来处理数据的，而变量就是用来存储数据的</strong></p></blockquote> <h2 id="目标"><a href="#目标" class="header-anchor">#</a> 目标</h2> <ul><li>变量定义</li> <li>变量的类型</li> <li>变量的命名</li></ul> <h2 id="_01-变量定义"><a href="#_01-变量定义" class="header-anchor">#</a> 01. 变量定义</h2> <ul><li>在 Python 中，每个变量 <strong>在使用前都必须赋值</strong>，变量 <strong>赋值以后</strong> 该变量 <strong>才会被创建</strong></li> <li>等号（=）用来给变量赋值
<ul><li><code>=</code> 左边是一个变量名</li> <li><code>=</code> 右边是存储在变量中的值</li></ul></li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>变量名 <span class="token operator">=</span> 值
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><blockquote><p>变量定义之后，后续就可以直接使用了</p></blockquote> <h3 id="_1-变量演练1-ipython"><a href="#_1-变量演练1-ipython" class="header-anchor">#</a> 1) 变量演练1 —— iPython</h3> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 定义 qq_number 的变量用来保存 qq 号码</span>
In <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">:</span> qq_number <span class="token operator">=</span> <span class="token string">&quot;1234567&quot;</span>

<span class="token comment"># 输出 qq_number 中保存的内容</span>
In <span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">:</span> qq_number
Out<span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">:</span> <span class="token string">'1234567'</span>

<span class="token comment"># 定义 qq_password 的变量用来保存 qq 密码</span>
In <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">:</span> qq_password <span class="token operator">=</span> <span class="token string">&quot;123&quot;</span>

<span class="token comment"># 输出 qq_password 中保存的内容</span>
In <span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">:</span> qq_password
Out<span class="token punctuation">[</span><span class="token number">4</span><span class="token punctuation">]</span><span class="token punctuation">:</span> <span class="token string">'123'</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br></div></div><blockquote><p>使用交互式方式，如果要查看变量内容，直接输入变量名即可，不需要使用 <code>print</code> 函数</p></blockquote> <h3 id="_2-变量演练-2-pycharm"><a href="#_2-变量演练-2-pycharm" class="header-anchor">#</a> 2) 变量演练 2 —— PyCharm</h3> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 定义 qq 号码变量</span>
qq_number <span class="token operator">=</span> <span class="token string">&quot;1234567&quot;</span>

<span class="token comment"># 定义 qq 密码变量</span>
qq_password <span class="token operator">=</span> <span class="token string">&quot;123&quot;</span>

<span class="token comment"># 在程序中，如果要输出变量的内容，需要使用 print 函数</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>qq_number<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>qq_password<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br></div></div><blockquote><p>使用解释器执行，如果要输出变量的内容，必须要要使用 <code>print</code> 函数</p></blockquote> <h3 id="_3-变量演练-3-超市买苹果"><a href="#_3-变量演练-3-超市买苹果" class="header-anchor">#</a> 3) 变量演练 3 —— 超市买苹果</h3> <blockquote><ul><li>可以用 <strong>其他变量的计算结果</strong> 来定义变量</li> <li>变量定义之后，后续就可以直接使用了</li></ul></blockquote> <p><strong>需求</strong></p> <ul><li>苹果的价格是 <strong>8.5 元/斤</strong></li> <li>买了 <strong>7.5 斤</strong> 苹果</li> <li>计算付款金额</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 定义苹果价格变量</span>
price <span class="token operator">=</span> <span class="token number">8.5</span>

<span class="token comment"># 定义购买重量</span>
weight <span class="token operator">=</span> <span class="token number">7.5</span>

<span class="token comment"># 计算金额</span>
money <span class="token operator">=</span> price <span class="token operator">*</span> weight

<span class="token keyword">print</span><span class="token punctuation">(</span>money<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br></div></div><h4 id="思考题"><a href="#思考题" class="header-anchor">#</a> 思考题</h4> <ul><li>如果 <strong>只要买苹果，就返 5 块钱</strong></li> <li>请重新计算购买金额</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 定义苹果价格变量</span>
price <span class="token operator">=</span> <span class="token number">8.5</span>

<span class="token comment"># 定义购买重量</span>
weight <span class="token operator">=</span> <span class="token number">7.5</span>

<span class="token comment"># 计算金额</span>
money <span class="token operator">=</span> price <span class="token operator">*</span> weight

<span class="token comment"># 只要买苹果就返 5 元</span>
money <span class="token operator">=</span> money <span class="token operator">-</span> <span class="token number">5</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>money<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br></div></div><p><strong>提问</strong></p> <ul><li>上述代码中，一共定义有几个变量？
<ul><li>三个：<code>price</code>／<code>weight</code>／<code>money</code></li></ul></li> <li><code>money = money - 5</code> 是在定义新的变量还是在使用变量？
<ul><li>直接使用之前已经定义的变量</li> <li>变量名 只有在 <strong>第一次出现</strong> 才是 <strong>定义变量</strong></li> <li>变量名 再次出现，不是定义变量，而是直接使用之前定义过的变量</li></ul></li> <li>在程序开发中，可以修改之前定义变量中保存的值吗？
<ul><li>可以</li> <li>变量中存储的值，就是可以 <strong>变</strong> 的</li></ul></li></ul> <h2 id="_02-变量的类型"><a href="#_02-变量的类型" class="header-anchor">#</a> 02. 变量的类型</h2> <ul><li>在内存中创建一个变量，会包括：
<ol><li>变量的名称</li> <li>变量保存的数据</li> <li>变量存储数据的类型</li> <li>变量的地址（标示）</li></ol></li></ul> <h3 id="_2-1-变量类型的演练-个人信息"><a href="#_2-1-变量类型的演练-个人信息" class="header-anchor">#</a> 2.1 变量类型的演练 —— 个人信息</h3> <p><strong>需求</strong></p> <ul><li>定义变量保存小明的个人信息</li> <li>姓名：<strong>小明</strong></li> <li>年龄：<strong>18</strong> 岁</li> <li>性别：<strong>是</strong>男生</li> <li>身高：<strong>1.75</strong> 米</li> <li>体重：<strong>75.0</strong> 公斤</li></ul> <blockquote><p>利用 <strong>单步调试</strong> 确认变量中保存数据的类型</p></blockquote> <p><strong>提问</strong></p> <ol><li>在演练中，一共有几种数据类型？
<ul><li>4 种</li> <li><code>str</code> —— 字符串</li> <li><code>bool</code> —— 布尔（真假）</li> <li><code>int</code> —— 整数</li> <li><code>float</code> —— 浮点数（小数）</li></ul></li> <li>在 <code>Python</code> 中定义变量时需要指定类型吗？
<ul><li>不需要</li> <li><code>Python</code> 可以根据 <code>=</code> 等号右侧的值，自动推导出变量中存储数据的类型</li></ul></li></ol> <h3 id="_2-2-变量的类型"><a href="#_2-2-变量的类型" class="header-anchor">#</a> 2.2 变量的类型</h3> <ul><li>在 <code>Python</code> 中定义变量是 <strong>不需要指定类型</strong>（在其他很多高级语言中都需要）</li> <li>数据类型可以分为 <strong>数字型</strong> 和 <strong>非数字型</strong></li> <li>数字型
<ul><li>整型 (<code>int</code>)</li> <li>浮点型（<code>float</code>）</li> <li>布尔型（<code>bool</code>）
<ul><li>真 <code>True</code> <code>非 0 数</code> —— <strong>非零即真</strong></li> <li>假 <code>False</code> <code>0</code></li></ul></li> <li>复数型 (<code>complex</code>)
<ul><li>主要用于科学计算，例如：平面场问题、波动问题、电感电容等问题</li></ul></li></ul></li> <li>非数字型
<ul><li>字符串</li> <li>列表</li> <li>元组</li> <li>字典</li></ul></li></ul> <blockquote><p>提示：在 Python 2.x 中，<strong>整数</strong> 根据保存数值的长度还分为：</p> <ul><li><code>int</code>（整数）</li> <li><code>long</code>（长整数）</li></ul></blockquote> <ul><li>使用 <code>type</code> 函数可以查看一个变量的类型</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>In <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">:</span> <span class="token builtin">type</span><span class="token punctuation">(</span>name<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h3 id="_2-3-不同类型变量之间的计算"><a href="#_2-3-不同类型变量之间的计算" class="header-anchor">#</a> 2.3 不同类型变量之间的计算</h3> <h4 id="_1-数字型变量-之间可以直接计算"><a href="#_1-数字型变量-之间可以直接计算" class="header-anchor">#</a> 1) <strong>数字型变量</strong> 之间可以直接计算</h4> <ul><li>在 Python 中，两个数字型变量是可以直接进行 算数运算的</li> <li>如果变量是 <code>bool</code> 型，在计算时
<ul><li><code>True</code> 对应的数字是 <code>1</code></li> <li><code>False</code> 对应的数字是 <code>0</code></li></ul></li></ul> <p><strong>演练步骤</strong></p> <ol><li>定义整数 <code>i = 10</code></li> <li>定义浮点数 <code>f = 10.5</code></li> <li>定义布尔型 <code>b = True</code></li></ol> <ul><li>在 iPython 中，使用上述三个变量相互进行算术运算</li></ul> <h4 id="_2-字符串变量-之间使用-拼接字符串"><a href="#_2-字符串变量-之间使用-拼接字符串" class="header-anchor">#</a> 2) <strong>字符串变量</strong> 之间使用 <code>+</code> 拼接字符串</h4> <ul><li>在 Python 中，字符串之间可以使用 <code>+</code> 拼接生成新的字符串</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>In <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">:</span> first_name <span class="token operator">=</span> <span class="token string">&quot;三&quot;</span>

In <span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">:</span> last_name <span class="token operator">=</span> <span class="token string">&quot;张&quot;</span>

In <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">:</span> first_name <span class="token operator">+</span> last_name
Out<span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">:</span> <span class="token string">'三张'</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br></div></div><h4 id="_3-字符串变量-可以和-整数-使用-重复拼接相同的字符串"><a href="#_3-字符串变量-可以和-整数-使用-重复拼接相同的字符串" class="header-anchor">#</a> 3) <strong>字符串变量</strong> 可以和 <strong>整数</strong> 使用 <code>*</code> 重复拼接相同的字符串</h4> <div class="language-python line-numbers-mode"><pre class="language-python"><code>In <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">:</span> <span class="token string">&quot;-&quot;</span> <span class="token operator">*</span> <span class="token number">50</span>
Out<span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">:</span> <span class="token string">'--------------------------------------------------'</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br></div></div><h4 id="_4-数字型变量-和-字符串-之间-不能进行其他计算"><a href="#_4-数字型变量-和-字符串-之间-不能进行其他计算" class="header-anchor">#</a> 4) <strong>数字型变量</strong> 和 <strong>字符串</strong> 之间 <strong>不能进行其他计算</strong></h4> <div class="language-python line-numbers-mode"><pre class="language-python"><code>In <span class="token punctuation">[</span><span class="token number">1</span><span class="token punctuation">]</span><span class="token punctuation">:</span> first_name <span class="token operator">=</span> <span class="token string">&quot;zhang&quot;</span>

In <span class="token punctuation">[</span><span class="token number">2</span><span class="token punctuation">]</span><span class="token punctuation">:</span> x <span class="token operator">=</span> <span class="token number">10</span>

In <span class="token punctuation">[</span><span class="token number">3</span><span class="token punctuation">]</span><span class="token punctuation">:</span> x <span class="token operator">+</span> first_name
<span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span><span class="token operator">-</span>
TypeError<span class="token punctuation">:</span> unsupported operand <span class="token builtin">type</span><span class="token punctuation">(</span>s<span class="token punctuation">)</span> <span class="token keyword">for</span> <span class="token operator">+</span><span class="token punctuation">:</span> <span class="token string">'int'</span> <span class="token keyword">and</span> <span class="token string">'str'</span>
类型错误：`<span class="token operator">+</span>` 不支持的操作类型：`<span class="token builtin">int</span>` 和 `<span class="token builtin">str</span>`
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><h3 id="_2-4-变量的输入"><a href="#_2-4-变量的输入" class="header-anchor">#</a> 2.4 变量的输入</h3> <ul><li>所谓 <strong>输入</strong>，就是 <strong>用代码</strong> <strong>获取</strong> 用户通过 <strong>键盘</strong> 输入的信息</li> <li>例如：去银行取钱，在 ATM 上输入密码</li> <li>在 Python 中，如果要获取用户在 <strong>键盘</strong> 上的输入信息，需要使用到 <code>input</code> 函数</li></ul> <h4 id="_1-关于函数"><a href="#_1-关于函数" class="header-anchor">#</a> 1) 关于函数</h4> <ul><li>一个 <strong>提前准备好的功能</strong>(别人或者自己写的代码)，<strong>可以直接使用</strong>，而 <strong>不用关心内部的细节</strong></li> <li>目前已经学习过的函数</li></ul> <table><thead><tr><th>函数</th> <th>说明</th></tr></thead> <tbody><tr><td>print(x)</td> <td>将 x 输出到控制台</td></tr> <tr><td>type(x)</td> <td>查看 x 的变量类型</td></tr></tbody></table> <h4 id="_2-input-函数实现键盘输入"><a href="#_2-input-函数实现键盘输入" class="header-anchor">#</a> 2) input 函数实现键盘输入</h4> <ul><li>在 Python 中可以使用 <code>input</code> 函数从键盘等待用户的输入</li> <li>用户输入的 <strong>任何内容</strong> Python 都认为是一个 <strong>字符串</strong></li> <li>语法如下：</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code>字符串变量 <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;提示信息：&quot;</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><h4 id="_3-类型转换函数"><a href="#_3-类型转换函数" class="header-anchor">#</a> 3) 类型转换函数</h4> <table><thead><tr><th>函数</th> <th>说明</th></tr></thead> <tbody><tr><td>int(x)</td> <td>将 x 转换为一个整数</td></tr> <tr><td>float(x)</td> <td>将 x 转换到一个浮点数</td></tr></tbody></table> <h4 id="_4-变量输入演练-超市买苹果增强版"><a href="#_4-变量输入演练-超市买苹果增强版" class="header-anchor">#</a> 4) 变量输入演练 —— 超市买苹果增强版</h4> <p><strong>需求</strong></p> <ul><li><strong>收银员输入</strong> 苹果的价格，单位：<strong>元／斤</strong></li> <li><strong>收银员输入</strong> 用户购买苹果的重量，单位：<strong>斤</strong></li> <li>计算并且 <strong>输出</strong> 付款金额</li></ul> <h5 id="演练方式-1"><a href="#演练方式-1" class="header-anchor">#</a> 演练方式 1</h5> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token comment"># 1. 输入苹果单价</span>
price_str <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入苹果价格：&quot;</span><span class="token punctuation">)</span>

<span class="token comment"># 2. 要求苹果重量</span>
weight_str <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入苹果重量：&quot;</span><span class="token punctuation">)</span>

<span class="token comment"># 3. 计算金额</span>
<span class="token comment"># 1&gt; 将苹果单价转换成小数</span>
price <span class="token operator">=</span> <span class="token builtin">float</span><span class="token punctuation">(</span>price_str<span class="token punctuation">)</span>

<span class="token comment"># 2&gt; 将苹果重量转换成小数</span>
weight <span class="token operator">=</span> <span class="token builtin">float</span><span class="token punctuation">(</span>weight_str<span class="token punctuation">)</span>

<span class="token comment"># 3&gt; 计算付款金额</span>
money <span class="token operator">=</span> price <span class="token operator">*</span> weight

<span class="token keyword">print</span><span class="token punctuation">(</span>money<span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br></div></div><p><strong>提问</strong></p> <ol><li>演练中，针对 <strong>价格</strong> 定义了几个变量？
<ul><li><strong>两个</strong></li> <li><code>price_str</code> 记录用户输入的价格字符串</li> <li><code>price</code> 记录转换后的价格数值</li></ul></li> <li><strong>思考</strong> —— 如果开发中，需要用户通过控制台 输入 <strong>很多个 数字</strong>，针对每一个数字都要定义两个变量，<strong>方便吗</strong>？</li></ol> <h5 id="演练方式-2-买苹果改进版"><a href="#演练方式-2-买苹果改进版" class="header-anchor">#</a> 演练方式 2 —— 买苹果改进版</h5> <ol><li><strong>定义</strong> 一个 <strong>浮点变量</strong> 接收用户输入的同时，就使用 <code>float</code> 函数进行转换</li></ol> <div class="language-python line-numbers-mode"><pre class="language-python"><code>price <span class="token operator">=</span> <span class="token builtin">float</span><span class="token punctuation">(</span><span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入价格:&quot;</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br></div></div><ul><li>改进后的好处：</li></ul> <ol><li>节约空间，只需要为一个变量分配空间</li> <li>起名字方便，不需要为中间变量起名字</li></ol> <ul><li>改进后的“缺点”：</li></ul> <ol><li>初学者需要知道，两个函数能够嵌套使用，稍微有一些难度</li></ol> <p><strong>提示</strong></p> <ul><li>如果输入的不是一个数字，程序执行时会出错，有关数据转换的高级话题，后续会讲！</li></ul> <h3 id="_2-5-变量的格式化输出"><a href="#_2-5-变量的格式化输出" class="header-anchor">#</a> 2.5 变量的格式化输出</h3> <blockquote><p>苹果单价 <code>9.00</code> 元／斤，购买了 <code>5.00</code> 斤，需要支付 <code>45.00</code> 元</p></blockquote> <ul><li>在 Python 中可以使用 <code>print</code> 函数将信息输出到控制台</li> <li>如果希望输出文字信息的同时，<strong>一起输出</strong> <strong>数据</strong>，就需要使用到 <strong>格式化操作符</strong></li> <li><code>%</code> 被称为 <strong>格式化操作符</strong>，专门用于处理字符串中的格式
<ul><li>包含 <code>%</code> 的字符串，被称为 <strong>格式化字符串</strong></li> <li><code>%</code> 和不同的 <strong>字符</strong> 连用，<strong>不同类型的数据</strong> 需要使用 <strong>不同的格式化字符</strong></li></ul></li></ul> <table><thead><tr><th>格式化字符</th> <th>含义</th></tr></thead> <tbody><tr><td>%s</td> <td>字符串</td></tr> <tr><td>%d</td> <td>有符号十进制整数，<code>%06d</code> 表示输出的整数显示位数，不足的地方使用 <code>0</code> 补全</td></tr> <tr><td>%f</td> <td>浮点数，<code>%.2f</code> 表示小数点后只显示两位</td></tr> <tr><td>%%</td> <td>输出 <code>%</code></td></tr></tbody></table> <ul><li>语法格式如下：</li></ul> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;格式化字符串&quot;</span> <span class="token operator">%</span> 变量<span class="token number">1</span><span class="token punctuation">)</span>

<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;格式化字符串&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>变量<span class="token number">1</span><span class="token punctuation">,</span> 变量<span class="token number">2.</span><span class="token punctuation">.</span><span class="token punctuation">.</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br></div></div><h4 id="格式化输出演练-基本练习"><a href="#格式化输出演练-基本练习" class="header-anchor">#</a> 格式化输出演练 —— 基本练习</h4> <p><strong>需求</strong></p> <ol><li>定义字符串变量 <code>name</code>，输出 <strong>我的名字叫 小明，请多多关照！</strong></li> <li>定义整数变量 <code>student_no</code>，输出 <strong>我的学号是 000001</strong></li> <li>定义小数 <code>price</code>、<code>weight</code>、<code>money</code>，输出 <strong>苹果单价 9.00 元／斤，购买了 5.00 斤，需要支付 45.00 元</strong></li> <li>定义一个小数 <code>scale</code>，输出 <strong>数据比例是 10.00%</strong></li></ol> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;我的名字叫 %s，请多多关照！&quot;</span> <span class="token operator">%</span> name<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;我的学号是 %06d&quot;</span> <span class="token operator">%</span> student_no<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;苹果单价 %.02f 元／斤，购买 %.02f 斤，需要支付 %.02f 元&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>price<span class="token punctuation">,</span> weight<span class="token punctuation">,</span> money<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;数据比例是 %.02f%%&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>scale <span class="token operator">*</span> <span class="token number">100</span><span class="token punctuation">)</span><span class="token punctuation">)</span>
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br></div></div><h4 id="课后练习-个人名片"><a href="#课后练习-个人名片" class="header-anchor">#</a> 课后练习 —— 个人名片</h4> <p><strong>需求</strong></p> <ul><li>在控制台依次提示用户输入：<strong>姓名</strong>、<strong>公司</strong>、<strong>职位</strong>、<strong>电话</strong>、<strong>邮箱</strong></li> <li>按照以下格式输出：</li></ul> <div class="language- line-numbers-mode"><pre class="language-text"><code>**************************************************
公司名称

姓名 (职位)

电话：电话
邮箱：邮箱
**************************************************
</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br></div></div><p>实现代码如下：</p> <div class="language-python line-numbers-mode"><pre class="language-python"><code><span class="token triple-quoted-string string">&quot;&quot;&quot;
在控制台依次提示用户输入：姓名、公司、职位、电话、电子邮箱
&quot;&quot;&quot;</span>
name <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入姓名：&quot;</span><span class="token punctuation">)</span>
company <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入公司：&quot;</span><span class="token punctuation">)</span>
title <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入职位：&quot;</span><span class="token punctuation">)</span>
phone <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入电话：&quot;</span><span class="token punctuation">)</span>
email <span class="token operator">=</span> <span class="token builtin">input</span><span class="token punctuation">(</span><span class="token string">&quot;请输入邮箱：&quot;</span><span class="token punctuation">)</span>

<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;*&quot;</span> <span class="token operator">*</span> <span class="token number">50</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span>company<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;%s (%s)&quot;</span> <span class="token operator">%</span> <span class="token punctuation">(</span>name<span class="token punctuation">,</span> title<span class="token punctuation">)</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;电话：%s&quot;</span> <span class="token operator">%</span> phone<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;邮箱：%s&quot;</span> <span class="token operator">%</span> email<span class="token punctuation">)</span>
<span class="token keyword">print</span><span class="token punctuation">(</span><span class="token string">&quot;*&quot;</span> <span class="token operator">*</span> <span class="token number">50</span><span class="token punctuation">)</span>

</code></pre> <div class="line-numbers-wrapper"><span class="line-number">1</span><br><span class="line-number">2</span><br><span class="line-number">3</span><br><span class="line-number">4</span><br><span class="line-number">5</span><br><span class="line-number">6</span><br><span class="line-number">7</span><br><span class="line-number">8</span><br><span class="line-number">9</span><br><span class="line-number">10</span><br><span class="line-number">11</span><br><span class="line-number">12</span><br><span class="line-number">13</span><br><span class="line-number">14</span><br><span class="line-number">15</span><br><span class="line-number">16</span><br><span class="line-number">17</span><br><span class="line-number">18</span><br></div></div></div></div> <!----> <div class="page-edit"><div class="edit-link"><a href="https://github.com/xugaoyi/vuepress-theme-vdoing/edit/master/docs/00.Python/08.变量的基本使用.md" target="_blank" rel="noopener noreferrer">编辑</a> <span><svg xmlns="http://www.w3.org/2000/svg" aria-hidden="true" focusable="false" x="0px" y="0px" viewBox="0 0 100 100" width="15" height="15" class="icon outbound"><path fill="currentColor" d="M18.8,85.1h56l0,0c2.2,0,4-1.8,4-4v-32h-8v28h-48v-48h28v-8h-32l0,0c-2.2,0-4,1.8-4,4v56C14.8,83.3,16.6,85.1,18.8,85.1z"></path> <polygon fill="currentColor" points="45.7,48.7 51.3,54.3 77.2,28.5 77.2,37.2 85.2,37.2 85.2,14.9 62.8,14.9 62.8,22.9 71.5,22.9"></polygon></svg> <span class="sr-only">(opens new window)</span></span></div> <!----> <!----></div> <div class="page-nav-wapper"><div class="page-nav-centre-wrap"><a href="/vdoing-demo-repository/pages/82298a/" class="page-nav-centre page-nav-centre-prev"><div class="tooltip">07_程序执行原理(科普)</div></a> <a href="/vdoing-demo-repository/pages/3e8319/" class="page-nav-centre page-nav-centre-next"><div class="tooltip">09_变量的命名</div></a></div> <div class="page-nav"><p class="inner"><span class="prev">
        ←
        <a href="/vdoing-demo-repository/pages/82298a/" class="prev">07_程序执行原理(科普)</a></span> <span class="next"><a href="/vdoing-demo-repository/pages/3e8319/">09_变量的命名</a>→
      </span></p></div></div></div> <!----></main></div> <div class="footer"><!----> 
  Theme by
  <a href="https://github.com/xugaoyi/vuepress-theme-vdoing" target="_blank" title="本站主题">Vdoing</a> 
    | Copyright © 2019-2023
    <span>Evan Xu | MIT License</span></div> <div class="buttons"><div title="返回顶部" class="button blur go-to-top iconfont icon-fanhuidingbu" style="display:none;"></div> <div title="去评论" class="button blur go-to-comment iconfont icon-pinglun" style="display:none;"></div> <div title="主题模式" class="button blur theme-mode-but iconfont icon-zhuti"><ul class="select-box" style="display:none;"><li class="iconfont icon-zidong">
          跟随系统
        </li><li class="iconfont icon-rijianmoshi">
          浅色模式
        </li><li class="iconfont icon-yejianmoshi">
          深色模式
        </li><li class="iconfont icon-yuedu">
          阅读模式
        </li></ul></div></div> <!----> <!----> <!----></div><div class="global-ui"></div></div>
    <script src="/vdoing-demo-repository/assets/js/app.52e6b5d0.js" defer></script><script src="/vdoing-demo-repository/assets/js/2.f10ddeba.js" defer></script><script src="/vdoing-demo-repository/assets/js/14.52e25550.js" defer></script>
  </body>
</html>
